Control apparatus for periodically energizing gaseous discharge devices



Feb. 22, 1949. H. A. ENGLE 2,462,371

, .CONTROL APPARATUS FOR PERIODICALLY ENERGIZING GASEOUS DISCHARGEDEVICES Filed March 19, 1947 W'J' w fig. 3.

INVENTOR. g

Patented Feb. 22, 1949 UNITED STATES PATENT OFFICE GONTROL APPARATUSFOR; PERIODICALLY ENERGIZING GASEOUS DISCHARGE DE- VICES.

Claims.

My invention relates to alternating current control apparatus of a typewhich serves to energize a load periodically at low frequency. Moreparticularly, my invention relates to improved. control apparatus forperiodically energizing neontype gaseous discharge devices.

One object of my invention is to provide an improved alternating currentcontrol apparatus which serves to vary the power supplied tow a loadperiodically without: employing contacts which make and break- Anotherobject of. my invention. is. to. provide. an improved. control apparatusof that type, for periodically exciting. a. neon.- type gaseousdischargedevice.

In accordance with my invention, I. employ a self-modulating resonantcircuit which includes an inductance coil. wound on an unsaturatedferromagnetic core and which. also includes. a thermally variableimpedance element which cooperates. with that inductance coil formodulating the current. which. flows in the. resonant circuit when theresonant circuit is connected to a source of A, C. (alternating current)potentials. In. one preferred embodiment of the. invention a loadcircuit which is to be controlled is inductively coupled with thatinductance coil and the amount of power supplied to this loadv circuitvaries in accordance with the amplitude of. the current flowing in the,resonant. circuit. Inv an.- other. preferred embodiment of theinvention, the modulated alternating current flowing. inthe resonantcircuit is rectified and the rectified current. is used to. vary thesaturation of a. saturable re.- actor in order to control the flow ofpower to a load. In the preferred. application. of my invention, Iemploy a resonant circuit of the type described to periodically excite,or energize, neontype gaseous dischargev devices such as neon signs.

The foregoing and other objects of my invention, together with numerousfeatures thereof, will be understood from thefollowing description takenin conjunction with the accompanying drawing, wherein- Figure 1'. is: aschematic wiring diagram of a circuit embodying my invention;

Fig. 2; is a schematic diagram of a similar circuit employing; avvoltage regulator at, the input; and

Big. 3 is. a schematic wiring diagram of. another embodiment of myinvention.

Referring to Fig. 1, there. is. illustrated a selfmodulating resonant.circuit in which. serves to periodically excite a. neon-type gaseous,discharge device l'l inductively coupled therewith. through, a voltagestep-up transformer l2. The.

resonant circuit II] is provided with an input 43 to which alternatingcurrent potentials are applied from some suitable source of A. C.potentials such as a cycle, volt power line, With the resonant circuit[0, constant amplitude A. C. potentials supplied from the power line areconverted into. modulated alternating current.

The resonant circuit I!) includes a rheostat I l, a thermally variableresistor i6, an adjustable condenser 20, and a first inductance coil 22,all connected in series with a second inductance coil comprising aprimary winding 24 of the transformer [2. The neon-type gaseousdischarge device I l is connected directly across the secondary winding32 of the transformer I 22. The variable. resistor l6. is of a typehaving a positive tem perature coeflicient of resistance, that is onewhosev resistance increases with temperature. The core 33 of thetransformer 121s preferably composed of iron or other ferromagneticmaterial, the permeability of which varies with the magnetizing force towhich it is subjected.

The various elements of the resonant circuit H! cooperate to modulatethe alternating current which. flows in the primary winding '24 at apredetermined pulsation frequency as more fully explainedhereinbelow.The modulation of the alternating current flowing in the resonantcircuit arises from the joint action of the variable impedancecharacteristics of the thermally variable resistor 15 and the primarywinding 24. The frequency of modulation depends in part upon thecharacteristics of the thermally variable resister [6 and the primarywinding 24 but may be varied by adjustment of therheostat M or thecondenser 20. By suitable adfiustment of the circuit constants; thefrequency of modulation can be established over av wide range of valuesfrom a few cycles. per second to one cycle every few minutes.

The transformer L2 is preferably of the closedcore type which perm-itssubstantial variation of the effective inductance of the primary winding24. as, a function of the currentflowing therein. In actual operation,the core is normally unmagnetizedv while no current is flowing in theprimarywinding 24 and is variably magnetized to values less thansaturation. when current is flowing; in; that winding. As a result, thepermeability of the core material varies from a minimum valuecorresponding to low alternating currents to. a maximumvaluecorresponding to largealternating currents. These. conditions aresatisfied if. the core is operated below the shoulder of themagnetization curve of the core material, and

particularly if the peak value of the minimum alternating currentmagnetizes the core to less than about 20% of saturation and the peakvalue of the maximum alternating current magnetizes the core to about50% to 80% of saturation. Saturation occurs above the shoulder of themagnetization curve and hence does not enter into the normal operationof this circuit.

Because the efiective permeability of the core 33 varies with theamplitude of the alternating current flowing in the primary winding 24,the effective impedance of this winding is not of con stant value butvaries as a direct function of the amplitude of the current flowingtherethrough. As a result, the resonant frequency of the resonantcircuit ii! is not constant but varies in a corresponding manner. Bytuning the resonant circuit In to a range of frequencies below thefrequency applied from the power line and operating the circuit at acurrent below the saturation value, the circuit becomes self-modulating.

The first inductance coil 22 serves to limit the current flowing in theresonant circuit It at least to the extent that its presence compensatessomewhat for poor regulation in the source of A. C. potentials. Thus, byincluding the first inductance coil 22 in series with the other elementsof the resonant circuit, the frequency of modulation of the alternatingcurrent flowing in the resonant circuit is more nearly constant than itwould otherwise be. For this purpose, the inductance coil 22 may be inthe form of a coi wound upon an iron core 34 having a small airgaptherein which operates at a substantially constant impedance throughoutthe entire cycle of modulation of the alternating urrent passingtherethrough. Preferably the inductance of the inductance coil 22 is ofa value intermediate the minimum and maximum values of the inductance ofthe primary winding 24.

In an alternative embodiment of the invention, the first inductance coil22 is of the closed-core type designed to operate as a variableimpedance device to modulate the current flowing therethrough in thesame manner as the primary winding 24 described hereinabove. But in thisembodiment of the invention, the core of the transformer I2 is providedwith suflicient iron for the inductance of the primary winding 24 toremain substantially constant throughout the range of currents passingtherethrough. However, both in this embodiment of the invention and thathereinabove described, the neon-type discharge lamp is coupled to theresonant circuit I ll through the voltage step-up transformer l2.

The turns-ratio of the secondary winding 32 to the primary winding 24 ishigh and of such value that the voltage applied to the gaseous dischargedevice ll periodically exceeds the ignition voltage thereof andperiodically falls below the extinction voltage. The minimum value ofturns-ratio required to excite the gaseous discharge device ll dependsupon its length as is well known. A suitable turns-ratio would be onefor which the gaseous discharge device is just ignited for the averagealternating current flowing in the primary winding 24. With thisarrangement, the gaseous discharge device H is periodically excited insynchronism with the modulation of the alternating current flowing inthe resonant circuit. More particularly, during the intervals when theamplitude of the alternatmg current flowing in the resonant circuit IQis low, the voltage applied to the gaseous discharge device II isinsuflicient to energize the gaseous discharge device and it remainsdark; but when the amplitude is high, the voltage impressed upon thegaseous discharge device H is likewise high and maintains it energizedand therefore glowing.

By the term neon-type gaseous discharge device, I mean to includegaseous discharge devices which operate on high voltage alternatingcurrent. As is well known, such a gaseous discharge device comprises anelongated envelope within which is sealed a gas, usually an inert gas,at low pressure. Such a gaseous discharge device includes a pair ofelectrodes disposed at opposite ends thereof between which current mayflow in either direction thus operating bilaterally.

In Fig. 2 I have illustrated an alternative embodiment of my inventionwhich is similar to the foregoing except that the first inductance coil22 is omitted and a voltage regulator 40 of the self-saturating type isconnected between the input it and the resonant circuit It. In this casethe presence of the regulator fill limits the Variation in modulationfrequency that would otherwise occur with changes in power line voltage.

It is to be understood that the control circuits illustrated can beoperated successfully without the aid Of the auxiliary inductance coil22 and without the aid of the regulating transformer 49, these twodevices serving only to stabilize the frequency of modulation in thepresence of variations in voltage applied to the input Id. The thermallyvariable resistor may be in the form of an incandescent lamp and ismerely one example of a thermally variable impedor which may be used inthe generation of the modulated alternating current. By the termthermally variable impedor I mean an impedance element, the impedance ofwhich varies as a continuous function of the current passingtherethrough, thus excluding from the term devices which open and closecontacts in accordance with changes of current flowing therein.

In Fig. 3 I have illustrated a circuit wherein the modulated alternatingcurrent is used to control the power flowing to a large load. Thiscircuit includes the same rheostat It, the same thermally variableresistor IS, the sam transformer l2, and the same adjustable capacitor26 connected as hereinabove described in connection with Fig. 1. In thiscase, however, the load to be controlled comprises two or more neontypegaseous discharge devices 50, each of which is connected across thesecondary winding 52 of a corresponding load transformer 54, the primarywindings 56 of which are all connected in paralnlel across the input l3of the resonant circuit In this case a saturable core reactor 60 havinga variable impedance winding 62 and a saturating winding 6d wound on asaturable core 66, is used to control the flow of power to the load inaccordance with current variations in the resonant circuit Ill. Theimpedance winding 62 is connected to the input l3 in series with theprimary windings 56 of the load transformers 54. The impedance of theimpedance winding 62 of the saturable core reactor 60 is controlled byvarying the direct current flowing in the saturating winding 56 thereofin accordance with the modulation of the alternating current in theresonant circuit 29. The application of direct current to the saturatingwinding is accomplished by means of a full-wave bridge rectifier 10comprising four rectifier elements 12 connected between the sec- .ondarywinding 32 .of the transformer l2 and the saturating winding 64.

A condenser 14 is preferably connected in parallel with the secondarywinding 32 inorder to tune the secondary winding to the frequency of thepower line so as to generate a large current therein.

The inclusion of the first inductance coil 22 in this circuit minimizesany tendency of load variation to affect the frequency of modulation.

In the operation of this circuit, the modulated alternating currentinduced in the secondary winding 32 of the transformer 12 is rectifiedby the rectifier Hi and the rectified current flows through thesaturating winding 64. With this arrangement the average direct currentflowing through the saturating winding 64% varies in sync-hronism withthe amplitude of the alternating current flowing in the resonant circuitIn and at the frequency of modulation.

When the current flowing in the saturating winding 64 is high, the core66 is highly saturated and the impedance of the impedance winding 62 isrelatively low, thus permitting a relatively large current to flow ineach of the primary wind ings 56 of the load transformers 54. On theother hand, when the current flowing in the saturating winding 64 islow, the core 66 is saturated to a lesser degree and the impedance ofthe impedance winding 62 is relatively high, thus permitting only arelatively low current to flow through the pri mary windings 56 of theload transformers 54.

Inasmuch as the voltage induced in the secondary winding 52 of each ofthe load transformers 54 is substantially proportional to the currentflowing in the primary winding thereof, it is thus seen that the voltageimpressed upon each of the gaseous discharge devices 50 variesperiodically at the frequency of modulation of the alternating currentflowing in the resonant circuit Ill. By selecting the turns-ratio of theprimary and secondary windings 56 and 52 of each of the transformers 54so that the minimum voltage impressed upon each of the gaseous dischargedevices 50 falls below the extinction voltage thereof and the maximumvoltage exceeds the ignition voltage thereof, the gaseous dischargedevices are periodically excited in synchronism with the modulation ofthe alternating current in the resonant circuit l0.

It is to be noted that the transformer I2 which is responsible for themodulation of the alternating current flowing in the resonant circuit isof conventional construction and operates without the aid of anymagnetic bias. It is also to be noted that the saturable core reactor 58takes no part in generating the modulated current and that this reactoris not a transformer since its two windings are not inductively coupled.Furthermore it is also to b noted that the periodic energization of theload is controlled solely in accordance with the modulation of thealternating current in the resonant circuit.

While I have described my invention as applied particularly to theperiodic control of the flow of electric power to neon-type gaseousdischarge devices, it is to be understood that my invention is alsoapplicable to the periodic control of alternating current power to othertypes of loads. Having now described several forms of apparatus in whichthe objects of my invention are attained, What I claim as new and desireto secure by Letters of Patent is'set forth in the appended claims.

I claim:

iii)

.1. .In combination: a transformer having a primary Winding and asecondary winding arranged on a ferromagnetic core; a resonant circuithaving an input adapted for connection to a source of A. C. potentials,said resonant circuit including said primary winding and a condenser; athermally variable impedance means operatively connected with saidprimary winding for varying th inductance thereof whereby the current inthe primary winding is modulated at a pulsation frequency lower than thefrequency of said A. C. potentials; and a load circuit connected acrosssaid secondary winding and periodically energized at the pulsationfrequency by th voltage induced therein from the primary winding.

2. In combination: a resonant circuit having an input adapted forconnection to a source of A. C. potentials, said resonant circuitincluding a condenser and an inductance coil wound on an unsaturatedferromagnetic core; a thermally vari able impedance means operativelyconnected with said inductance coil for modulating the current flowingin said resonant circuit at a pulsation frequency lower than thefrequency of said A. C. potentials; and a load circuit inductivelycoupled with said inductance coil and controlled in accordance with theamplitude of the current flowing in said resonant circuit whereby thevoltage supplied to said load circuit varies in synchronism therewith.

3. In combination: a transformer having a pri mary winding and asecondary winding arranged on an unsaturated ferromagnetic core; aresonant circuit having an input adapted for connection to a source ofA. C. potentials, said resonant circuit including said primary windingand a condenser; a thermally variable impedance means operativelyconnected with said primary winding for modulating the current in theprimary winding at a pulsation frequency lower than the fre-- quency ofsaid A. C. potentials; and a load circuit connected to said secondarywinding and controlled solely by the voltage induced therein by currentflowing in the primary winding whereby t the voltage supplied to saidload circuit varies in synchronism with amplitude of the alternatingcurrent flowing in said primary winding.

4. In combination: a resonant circuit having an input adapted forconnection to a source of A. C. potentials, said resonant circuitincluding a condenser and an inductance coil Wound on an unsaturatedferromagnetic core; a thermally variable impedance means operativelyconnected with said inductance coil for modulating the current flowingin said resonant circuit at a pulsation frequency lower than thefrequency of said A. C. potentials; and a neon-type gaseous clischargedevice inductively coupled with said inductance coil and periodicallyenergized at the pulsation frequency by the voltage induced therein bycurrent flowing in the primary windmg.

5. In combination: transformer having a primary winding and a secondarywinding arranged on an unsaturated ferromagnetic core, the turnsratio ofsaid secondary and primary windings being high; a resonant circuithaving an input adapted for a connection to a source of A. C.potentials, said resonant circuit including said primary winding and acondenser; a thermally variable impedance means operatively connectedwith said primary winding for modulating the current in the primarywinding at a pulsation frequency lower than the frequency of said A. C.potentials; and a neon-type gaseous discharge device connected acrosssaid secondary windingand periodically energized at the pulsationfrequency by the voltage induced therein by current flowing in theprimary winding. v

6. In combination: a first transformer having a primary winding and asecondary winding arranged on an unsaturated ferromagnetic core; aresonant circuit having an input adapted for connection to a source ofA. C. potentials, said resonant circuit including said primary windingand a condenser; a thermally variable impedance means operativelyconnected with said primary winding for modulating the current in theprimary winding at a pulsation frequency lower than the frequency ofsaid A. C. potentials; a second transformer having a primary winding anda secondary winding; a saturable reactorvhaving an impedance winding anda saturating winding; the primary winding of said second transformer andthe impedance winding of said saturable reactor being connected in acommon circuit across said input; a load circuit connected to thesecondary winding of said second transformer; and a rectifier connectedbetween the secondary winding of said first transformer and saidsaturating winding for varying the degree of saturation of saidsaturable reactor whereby the power supplied to said load circuit variesin accordance with the modulation of the current in the primary windingof said first transformer.

7. In combination: a first transformer having a primary winding and asecondary winding arranged on an unsaturated ferromagnetic core; aresonant circuit having an input adapted for connection to a source ofA. C. potentials, said resonant circuit including said primary windingand a condenser; a thermally variable impedance means operativelyconnected with said primary winding for modulating the current in theprimary winding at a pulsation frequency lower than the frequency ofsaid A. C. potentials; a plurality of second transformers, each having aprimary winding and a secondary winding, the turns-ratio of the lattersecondary and primary windings being high; a saturable reactor having animpedance winding and a saturatin winding; the primary windings of saidsecond transformers and the impedance winding of said saturable reactorbeing connected in a common circuit across said input; and a pluralityof "neon-type gaseous discharge device connected across the respectivesecondary windings of said second transformers; and a rectifierconnected between the secondary winding of said. first transformer andsaid saturating winding for varying the saturation of saidsatur'ablereactor whereby said gaseous discharge devices are periodicallyenergized at the pulsation frequency in synchronism with the modulationof the current flowing in said resonant circuit.

8. In combination: a transformer having a primary windin and a secondarywinding arranged on a ferromagnetic core; a resonant circuit having aninput adapted for connection to a source of A. C. potentials, saidresonant circuit including said primary winding and a condenser;thermally variable impedance means operatively connected with saidprimary winding for varying the inductance thereof whereby the currentin the pri mary winding is modulated at a pulsation frequency lower thanthe frequency of said A. C. potentials; and a load circuit periodicallyenergized at the pulsation frequency by the voltage induced in saidsecondary winding by the modulated current flowing in said primarywinding.

9. In combination: a transformer having a primary Winding and asecondary winding arranged on a ferromagnetic core; a resonant circuithaving an input adapted for connection to a source of A. C. potentials,said resonant circuit including said-primary winding and a condenser;thermally variable impedance means operatively connected with saidprimary winding for varying the inductance thereof whereby the currentin the primary winding is modulated at a pulsation frequency lower thanthe frequency of said A.'C.. potentials; and a load circuit periodicallyenergized at said pulsation frequency by the voltage induced in saidsecondary winding. 10. In combination: a transformer having a primarywinding and a secondary winding arranged on a ferromagnetic core; aresonant circuit having an input adapted for connection to a source ofA. C. potentials, said resonant circuit including said primary windingand a condenser; thermally variable impedance means operativelyconnected with said primary winding for varying the inductance thereofwhereby the current in the primary winding is modulated at a pulsationfrequency lower than the frequency of said A. C, potentials; and aneon-type gaseous discharge device periodically energized at saidpulsation frequency by the voltage induced in said secondary winding bythe current flowing in said primary winding.

HOMER A. ENGLE.

No references cited.

